Subject: Re: bug#28258: 26.0.50; [PATCH] Let file-name-base succeed when buffer-file-name is nil

From: Philipp Stephani <[email-masked]>
Date: Mon, 18 Sep 2017 17:12:36 +0000

Glenn Morris <[email-masked]> schrieb am Di., 29. Aug. 2017 um 19:03 Uhr:

> Mohammed Sadiq wrote:
>
> >> IIUC: file-name-base currently errors when called with no applicable
> >> file name, and you want it to instead return nil? This seems rather
> >> unusual for an Emacs file-related function. I would have thought this
> >> unlikely to be applied, but maybe you could explain why you want it?
> >
> > The signature of `file-name-base' is (file-name-base &optional FILENAME).
> > That is, the FILENAME argument is optional. So I believe it shouldn't
> > be an error to not give the optional argument. And so calling the
> function
> > in a buffer with no file associated shouldn't be an error. I'm not sure
> > if my assertion is right.
>
> Thanks for explaining. I don't think I agree, but then the fact that the
> argument is optional and defaults to buffer-file-name also seems
> atypical to me (eg I don't think any other file-name- functions behaves
> like that). Let's wait and see if anyone else feels strongly one way or
> the other.
>
>
>
>
Changing from raising an error to returning nil is a breaking change:
callers currently can rely on the return value being never nil, and can
rely on errors being raised. Changing this would break these assumptions.
Even ignoring that, I think raising an error is the right thing to do:
unless given a filename, the function can't fulfil its promise, and raising
an error is the most appropriate reaction to this. (There are already way
too many Elisp functions that silently ignore errorneous situations.)
I do agree that the calling convention of `file-name-base' is odd. How
about making the argument mandatory (initially only by changing the
advertised calling convention and the docstring)?